The torque wrench has been a staple of the mechanic's tool chest for perhaps a hundred years or more. As would be familiar to those of ordinary skill, a torque wrench is a wrench used to precisely set the torque of a threaded fastening item such as a nut or a bolt. Torque wrenches are used where the tightness of fasteners is crucial, allowing the operator to measure and/or control the amount of torque applied to the fastening device so that it can be matched to specifications.
The application, measurement and retention of information relative to the torque applied to various mechanical items becomes increasingly important for increasingly complex mechanical devices and systems. Accurate, precise and controlled application of torsion force (torque) is increasingly required for many applications involving safety considerations as well as regulatory, investigative, and production process tracking and audit trails, in addition to merely ensuring that a system whose reliable operation depends upon correct application of torsional force to its components. Further, the range of environments in which torque wrenches are used varies widely, and influences the ability of the tool operator to reliably and repeatedly apply torque to a system.
A common type of torque wrench is referred to as a “beam-type” torque wrench. In general, a beam-type torque wrench comprises an elongate lever arm (beam) having a handle on a proximal end and a wrench head (socket) at a distal end for engaging an item to which torsional force is applied. The beam is made of a material which will flex elastically along its length under applied force. A second, smaller bar carrying an indicator is connected to the distal end of the beam and extends substantially in parallel with the beam toward the proximal end. The proximal end of the second arm is not secured to the main beam, and hence is not subjected to strain and remains straight during use of the wrench. A calibrated scale is fitted to the handle in proximity to the proximal end of the second arm. The bending of the main beam under application of force causes the scale to move under the proximal end of the second arm. When the desired indicated torque is reached, the operator stops applying force.
Reading the displacement of the beam, which is the measure of the amount of torque applied, is the most important feature of the digital beam torque wrench. The repeatability of the displacement of the standard beam type torque wrench has been established. The beam torque wrench has the ability to be more accurate and repeatable than other conventional and/or more expensive torque wrench technology. However, a potential problem with existing beam type torque wrenches lies in the difficulty of the human eye in discriminating the rather limited displacement of the beam relative to the indicator.
It is believed, therefore, that there remains a need for a torque wrench that can be efficiently read with a high degree of accuracy. Moreover, there is an increasing need for torque wrenches having additional functional capabilities, such as providing additional forms of readout (for example, visual, and/or audible), and/or providing a means for recording, storing, and perhaps transmitting measured torque values.